Browsing by Subject "NUCLEI"

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  • Boguslavski, K.; Kurkela, A.; Lappi, Tuomas; Peuron, Jarkko (2021)
    Motivated by the initial stages of high-energy heavy-ion collisions, we study excitations of far-from-equilibrium 2+1 dimensional gauge theories using classical-statistical lattice simulations. We evolve field perturbations over a strongly overoccupied background undergoing self-similar evolution. While in 3+1D the excitations are described by hard-thermal loop theory, their structure in 2+1D is nontrivial and nonperturbative. These nonperturbative interactions lead to broad excitation peaks in spectral and statistical correlation functions. Their width is comparable to the frequency of soft excitations, demonstrating the absence of soft quasiparticles in these theories. Our results also suggest that excitations at higher momenta are sufficiently long-lived, such that an effective kinetic theory description for 2+1 dimensional Glasma-like systems may exist, but its collision kernel must be nonperturbatively determined.
  • Pakarinen, J.; Grahn, T.; Gaffney, L. P.; Algora, A.; Bauer, C.; Blazhev, A.; Bree, N.; Cocolios, T. E.; De Witte, H.; Diriken, J.; Fernier, P.; K, Hadynska-Kle K.; Herzan, A.; Huyse, M.; Iwanicki, J.; Jakobsson, Ulrika; Jenkins, D.; Kesteloot, N.; Konki, J.; Lannoo, B.; Papadakis, P.; Peura, P.; Rahkila, P.; Rainovski, G.; Rapisarda, E.; Reiter, P.; Sambi, S.; Scheck, M.; Seibeck, B.; Seidlitz, M.; Stora, T.; Van Duppen, P.; Warr, N.; Wenander, F.; Vermeulen, M. J.; Voulot, D.; Wrzosek-Lipska, K.; Zielinska, M. (2017)
    The neutron-deficient Pb-196,Pb-198 isotopes have been studied in Coulomb-excitation experiments employing the Miniball gamma-ray spectrometer and radioactive ion beams from the REX-ISOLDE post-accelerator at CERN. The reduced transition probabilities of the first excited 2(+) states in Pb-196 and Pb-198 nuclei have been measured for the first time. Values of B (E2) = 18.2(-4.1)(+4.8) W. u. and B (E2) = 13.1(-3.5)(+4.9) W. u., were obtained, respectively. The experiment sheds light on the development of collectivity when moving from the regime governed by the generalised seniority scheme to a region, where intruding structures, associated with different deformed shapes, start to come down in energy and approach the spherical ground state.
  • Dobaczewski, Jacek; Engel, Jonathan; Kortelainen, Markus; Becker, Pierre (2018)
    We show that the measured intrinsic octupole moments of Rn-220, Ra-224, and Ra-226 constrain the intrinsic Schiff moments of Ra-225, Rn-221, Rn-223, Fr-223, Ra-225, and Pa-229. The result is a dramatically reduced uncertainty in intrinsic Schiff moments. Direct measurements of octupole moments in odd nuclei will reduce the uncertainty even more. The only significant source of nuclear-physics error in the laboratory Schiff moments will then be the intrinsic matrix elements of the time-reversal noninvariant interaction produced by CP-violating fundamental physics. Those matrix elements are also correlated with octupole moments, but with a larger systematic uncertainty.
  • Ertoprak, A.; Cederwall, B.; Qi, C.; Aktas, O.; Doncel, M.; Hadinia, B.; Liotta, R.; Sandzelius, M.; Scholey, C.; Andgren, K.; Back, T.; Badran, H.; Braunroth, T.; Calverley, T.; Cox, D. M.; Cullen, D. M.; Fang, Y. D.; Ganioglu, E.; Giles, M.; Gomez Hornillos, M. B.; Grahn, T.; Greenlees, P. T.; Hilton, J.; Hodge, D.; Ideguchi, E.; Jakobsson, U.; Johnson, A.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S.; Khaplanov, A.; Kumar Raju, M.; Leino, M.; Li, H.; Liu, H.; Matta, S.; Modamio, V.; Nara Singh, B. S.; Niikura, M.; Nyman, M.; Ozgur, I.; Page, R. D.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Paul, E. S.; Petrache, C. M.; Peura, P.; Rahkila, P.; Ruotsalainen, P.; Saren, J.; Sorri, J.; Stolze, S.; Subramaniam, P.; Taylor, M. J.; Uusitalo, J.; Valiente-Dobon, J. J.; Wyss, R. (2020)
    Excited states in the extremely neutron-deficient nucleus Pt-172 were populated via Ru-96(Kr-78, 2p) and Mo-92(Kr-83, 3n) reactions. The level scheme has been extended up to an excitation energy of approximate to 5MeV and tentative spin-parity assignments up to I-pi = 18(+). Linear polarization and angular distribution measurements were used to determine the electromagnetic E1 character of the dipole transitions connecting the positive-parity ground-state band with an excited side-band, firmly establishing it as a negativeparity band. The lowestmember of this negative-parity structure was firmly assigned spin-parity 3(-). In addition, we observed an E3 transition from this 3(-) state to the ground state, providing direct evidence for octupole collectivity in Pt-172. Large-scale shell model (LSSM) and total Routhian surface (TRS) calculations have been performed, supporting the interpretation of the 3(-) state as a collective octupole-vibrational state.
  • IDS Collaboration; Lica, R.; Greenlees, P. T.; Konki, J.; Rahkila, P. (2018)
    The occurrence of octupolar shapes in the Ba isotopic chain was recently established experimentally up to N = 90. To further extend the systematics, the evolution of shapes in the most neutron-rich members of the Z = 56 isotopic chain accessible at present, Ba-148,Ba-150, has been studied via beta decay at the ISOLDE Decay Station. This paper reports on the first measurement of the positive-and negative-parity low-spin excited states of 150Ba and presents an extension of the beta-decay scheme of Cs-148. Employing the fast timing technique, half-lives for the 2(1)(+) level in both nuclei have been determined, resulting in T-1/2 = 1.51(1) ns for Ba-148 and T-1/2 = 3.4(2) ns for Ba-150. The systematics of low-spin states, together with the experimental determination of the B(E2 : 2(+) -> 0(+)) transition probabilities, indicate an increasing collectivity in Ba148-150, towards prolate deformed shapes. The experimental data are compared to symmetry conserving configuration mixing (SCCM) calculations, confirming an evolution of increasingly quadrupole deformed shapes with a definite octupolar character.
  • Äystö, J.; Behr, K. -H.; Benlliure, J.; Bracco, A.; Egelhof, P.; Fomichev, A.; Gales, S.; Geissel, H.; Grahn, T.; Grigorenko, L. V.; Harakeh, M. N.; Hayano, R.; Heinz, S.; Itahashi, K.; Jokinen, A.; Kalantar-Nayestanaki, N.; Kanungo, R.; Lenske, H.; Mukha, I.; Muenzenberg, G.; Nociforo, C.; Ong, H. J.; Pietri, S.; Pfutzner, M.; Plass, W.; Prochazka, A.; Purushothaman, S.; Saito, T.; Scheidenberger, C.; Simon, H.; Tanihata, I.; Terashima, S.; Toki, H.; Trache, L.; Weick, H.; Winfield, J. S.; Winkler, M.; Zamfir, V.; Super-FRS Collaboration NUSTAR (2016)
    The physics program at the super-conducting fragment separator (Super-FRS) at FAIR, being operated in a multiple-stage, high-resolution spectrometer mode, is discussed. The Super-FRS will produce, separate and transport radioactive beams at high energies up to 1.5 AGeV, and it can be also used as a stand-alone experimental device together with ancillary detectors. Various combinations of the magnetic sections of the Super-FRS can be operated in dispersive, achromatic or dispersion-matched spectrometer ion-optical modes, which allow measurements of momentum distributions of secondary-reaction products with high resolution and precision. A number of unique experiments in atomic, nuclear and hadron physics are suggested with the Super-FRS as a stand-alone device, in particular searches for new isotopes, studies of hyper-nuclei, delta-resonances in exotic nuclei and spectroscopy of atoms characterized by bound mesons. Rare decay modes like multiple-proton or neutron emission and the nuclear tensor force observed in high momentum regime can be also addressed. The in-flight radioactivity measurements as well as fusion, transfer and deep-inelastic reaction mechanisms with the slowed-down and energy-bunched fragment beams are proposed for the high-resolution and energy buncher modes at the Super-FRS. (C) 2016 Elsevier B.V. All rights reserved.
  • Kontkanen, Jenni; Olenius, Tinja; Kulmala, Markku; Riipinen, Ilona (2018)
    Atmospheric new particle formation (NPF) occurs by the formation of nanometer-sized molecular clusters and their subsequent growth to larger particles. NPF involving sulfuric acid, bases and oxidized organic compounds is an important source of atmospheric aerosol particles. One of the mechanisms suggested to depict this process is nano-Kohler theory, which describes the activation of inorganic molecular clusters to growth by a soluble organic vapor. In this work, we studied the capability of nano-Kohler theory to describe the initial growth of atmospheric molecular clusters by simulating the dynamics of a cluster population in the presence of a sulfuric acid-base mixture and an organic compound. We observed nano-Kohler-type activation in our simulations when the saturation ratio of the organic vapor and the ratio between organic and inorganic vapor concentrations were in a suitable range. However, nano-Kohler theory was unable to predict the exact size at which the activation occurred in the simulations. In some conditions, apparent cluster growth rate (GR) started to increase close to the activation size determined from the simulations. Nevertheless, because the behavior of GR is also affected by other dynamic processes, GR alone cannot be used to deduce the cluster growth mechanism.
  • Gottardo, A.; Verney, D.; Delafosse, C.; Ibrahim, F.; Roussiere, B.; Sotty, C.; Roccia, S.; Andreoiu, C.; Costache, C.; Delattre, M. -C.; Deloncle, I.; Etile, A.; Franchoo, S.; Gaulard, C.; Guillot, J.; Lebois, M.; MacCormick, M.; Marginean, N.; Marginean, R.; Matea, I.; Mihai, C.; Mitu, I.; Olivier, L.; Portail, C.; Qi, L.; Stan, L.; Testov, D.; Wilson, J.; Yordanov, D. T. (2016)
    The N = 48 Ge-80 nucleus is studied by means of beta-delayed electron-conversion spectroscopy at ALTO. The radioactive Ga-80 beam is produced through the isotope separation on line photofission technique and collected on a movable tape for the measurement of gamma and e(-) emission following beta decay. An electric monopole E0 transition, which points to a 639(1) keV intruder 0(2)(+) state, is observed for the first time. This new state is lower than the 2(1)(+) level in Ge-80, and provides evidence of shape coexistence close to one of the most neutron-rich doubly magic nuclei discovered so far, Ni-78. This result is compared with theoretical estimates, helping to explain the role of monopole and quadrupole forces in the weakening of the N = 50 gap at Z = 32. The evolution of intruder 0(2)(+) states towards Ni-78 is discussed.
  • Adams, Michael P.; Atanasova, Nina S.; Sofieva, Svetlana; Ravantti, Janne; Heikkinen, Aino; Brasseur, Zoe; Duplissy, Jonathan; Bamford, Dennis H.; Murray, Benjamin J. (2021)
    In order to effectively predict the formation of ice in clouds we need to know which subsets of aerosol particles are effective at nucleating ice, how they are distributed and where they are from. A large proportion of ice-nucleating particles (INPs) in many locations are likely of biological origin, and some INPs are extremely small, being just tens of nanometres in size. The identity and sources of such INPs are not well characterized. Here, we show that several different types of virus particles can nucleate ice, with up to about 1 in 20 million virus particles able to nucleate ice at -20 degrees C. In terms of the impact on cloud glaciation, the ice-nucleating ability (the fraction which are ice nucleation active as a function of temperature) taken together with typical virus particle concentrations in the atmosphere leads to the conclusion that virus particles make a minor contribution to the atmospheric ice-nucleating particle population in the terrestrial-influenced atmosphere. However, they cannot be ruled out as being important in the remote marine atmosphere. It is striking that virus particles have an ice-nucleating activity, and further work should be done to explore other types of viruses for both their ice-nucleating potential and to understand the mechanism by which viruses nucleate ice.
  • Lica, R.; Rotaru, F.; Borge, M. J. G.; Grevy, S.; Negoita, F.; Poves, A.; Sorlin, O.; Andreyev, A. N.; Borcea, R.; Costache, C.; De Witte, H.; Fraile, L. M.; Greenlees, P. T.; Huyse, M.; Ionescu, A.; Kisyov, S.; Konki, J.; Lazarus, I.; Madurga, M.; Marginean, N.; Marginean, R.; Mihai, C.; Mihai, R. E.; Negret, A.; Page, R. D.; Pakarinen, J.; Pascu, S.; Pucknell, V.; Rahkila, P.; Rapisarda, E.; Serban, A.; Sotty, C. O.; Stan, L.; Stanoiu, M.; Tengblad, O.; Turturica, A.; Van Duppen, P.; Wadsworth, R.; Warr, N.; IDS Collaboration (2017)
    The beta(-) decay of Mg-34 was used to study the Al-34 nucleus through. spectroscopy at the Isotope Separator On-Line facility of CERN. Previous studies identified two beta-decaying states in Al-34 having spin-parity assignments J(pi) = 4(-) dominated by the normal configuration pi(d(5/2))(-1)circle times nu(f(7/2)) and J(pi) = 1(+) by the intruder configuration pi(d(5/2))(-1) circle times nu(d(3/2))(-1) (f(7/2))(2). Their unknown ordering and relative energy have been the subject of debate for the placement of Al-34 inside or outside the N = 20 "island of inversion." We report here that the 1(+) intruder lies only 46.6 keV above the 4(-) ground state. In addition, a new half-life of T-1/2 = 44.9(4) ms, that is twice as long as the previously measured 20(10) ms, has been determined for Mg-34. Large-scale shell-model calculations with the recently developed SDPF-U-MIX interaction are compared with the new data and used to interpret the mechanisms at play at the very border of the N = 20 island of inversion.
  • Besel, Vitus; Kubecka, Jakub; Kurten, Theo; Vehkamäki, Hanna (2020)
    We tested the influence of various parameters on the new particle formation rate predicted for the sulfuric acid–ammonia system using quantum chemistry and cluster distribution dynamics simulations, in our case, Atmospheric Cluster Dynamics Code (ACDC). We found that consistent consideration of the rotational symmetry number of monomers (sulfuric acid and ammonia molecules, and bisulfate and ammonium ions) leads to a significant rise in the predicted particle formation rate, whereas inclusion of the rotational symmetry number of the clusters only changes the results slightly, and only in conditions where charged clusters dominate the particle formation rate. This is because most of the clusters stable enough to participate in new particle formation have a rotational symmetry number of 1, and few exceptions to this rule are positively charged clusters. In contrast, the application of the quasi-harmonic correction for low-frequency vibrational modes tends to generally decrease predicted new particle formation rates and also significantly alters the slope of the formation rate curve plotted against the sulfuric acid concentration, which is a typical convention in atmospheric aerosol science. The impact of the maximum size of the clusters explicitly included in the simulations depends on the simulated conditions. The errors arising from a limited set of clusters are higher for higher evaporation rates, and thus tend to increase with temperature. Similarly, the errors tend to be higher for lower vapor concentrations. The boundary conditions for outgrowing clusters (that are counted as formed particles) have only a small influence on the results, provided that the definition is chemically reasonable and that the set of simulated clusters is sufficiently large. A comparison with data from the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber and a cluster distribution dynamics model using older quantum chemistry input data shows improved agreement when using our new input data and the proposed combination of symmetry and quasi-harmonic corrections.
  • Tuovinen, Saana; Kontkanen, Jenni; Jiang, Jingkun; Kulmala, Markku (2020)
    New Particle Formation (NPF) is regularly observed to occur in heavily polluted Chinese megacities. However, in these NPF events, the survival probability of small clusters into larger aerosol particles is higher than theoretically predicted. One explanation for this could be that the loss rate of clusters due to scavenging by pre-existing particles, which is described by condensation sink, is lower than expected. In this study, we describe the loss of clusters due to condensation sink by using heterogeneous nucleation theory, and investigate if ineffectiveness of heterogeneous nucleation can result in a significantly lowered effective condensation sink. We find that in principle it is possible that due to properties of the system there is no heterogeneous nucleation, and this can significantly influence the magnitude of effective condensation sink and thus increase the survival probability of clusters.
  • Singh, B. S. Nara; Cullen, D. M.; Taylor, M. J.; Srivastava, P. C.; Van Isacker, P.; Beeke, O.; Dodson, B.; Scholey, C.; O'Donell, D.; Jakobson, U.; Grahn, T.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Khan, S.; Leino, M.; Leppänen, A-P.; Eeckhaudt, S.; Mäntyniemi, K.; Pakarinen, J.; Peura, P.; Rahkila, P.; Saren, J.; Sorri, J.; Uusitalo, J.; Venhart, M. (2018)
    Excited states above the 17(+) isomeric state in the proton-rich nucleus Tm-152 were established by employing the recoil-isomer tagging technique. Data were collected using the JUROGAM gamma-ray array and the GREAT spectrometer together with the recoil ion transport unit (RITU) gas-filled recoil separator and analyzed to identify the prompt and delayed gamma decays from the levels in Tm-152. Shell-model calculations, either in a large valence space or in a reduced model space with five protons in the pi 0h(11)(/2) orbital and one neutron in the nu 1 f(7/2) orbital, agree with the observed energies of the yrast levels up to angular momentum J = 21. The observation of near degeneracies in the energy spectrum can be attributed to specific components of the proton-neutron interaction. The isomeric decay of the 17(+) level is not reproduced in the shell-model calculations as it arises from a delicate balance between hindrance due to seniority selection rules and enhancement due to configuration mixing.
  • Norris, S. J.; Brooks, I. M.; Moat, B. I.; Yelland, M. J.; de Leeuw, G.; Pascal, R. W.; Brooks, B. (2013)
  • Kuerten, Andreas; Jokinen, Tuija; Simon, Mario; Sipilä, Mikko; Sarnela, Nina; Junninen, Heikki; Adamov, Alexey; Almeida, Joao; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Hutterli, Manuel; Kangasluoma, Juha; Kirkby, Jasper; Laaksonen, Ari; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Mathot, Serge; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schobesberger, Siegfried; Seinfeld, John H.; Steiner, Gerhard; Tome, Antonio; Troestl, Jasmin; Winkler, Paul M.; Williamson, Christina; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Kenneth S.; Kulmala, Markku; Worsnop, Douglas R.; Curtius, Joachim (2014)
  • Bennaceur, K.; Idini, A.; Dobaczewski, J.; Dobaczewski, P.; Kortelainen, M.; Raimondi, F. (2017)
    We propose to use two-body regularized finite-range pseudopotential to generate nuclear energy density functional (EDF) in both particle-hole and particle-particle channels, which makes it free from self-interaction and selfpairing, and also free from singularities when used beyond mean field. We derive a sequence of pseudopotentials regularized up to next-to-leading order and next-to-next-to-leading order, which fairly well describe infinite-nuclearmatter properties and finite open-shell paired and/or deformed nuclei. Since pure two-body pseudopotentials cannot generate sufficiently large effective mass, the obtained solutions constitute a preliminary step towards future implementations, which will include, e.g., EDF terms generated by three-body pseudopotentials.
  • IDS Collaboration; Lica, R. (2019)
    The structure of Si-34 was studied through gamma spectroscopy separately in the beta(-) decays of Mg-34 and Al-34 at the ISOLDE facility of CERN. Different configurations in Si-34 were populated independently from the two recently identified beta-decaying states in Al-34 having spin-parity assignments J(pi) = 4(-) dominated by the normal configuration pi(d(5/2))(-1) circle times nu(f(7/2)) and J(pi) = 1(+) by the intruder configuration pi(d(5/2))(-1) circle times nu(d(3/2))(-1) (f(7/2))(2). The paper reports on spectroscopic properties of Si-34 such as an extended level scheme, spin and parity assignments based on log(ft) values and gamma-ray branching ratios, absolute beta feeding intensities, and neutron emission probabilities. A total of 11 newly identified levels and 26 transitions were added to the previously known level scheme of Si-34. Large scale shell-model calculations using the SDPF-U-MIX interaction, able to treat higher order intruder configurations, are compared with the new results and conclusions are drawn concerning the predictive power of SDPF-U-MIX, the N = 20 shell gap, the level of mixing between normal and intruder configurations for the 0(1)(+), 0(2)(+), and 2(1)(+) states, and the absence of triaxial deformation in Si-3(4).
  • Wang, Kai; Kortelainen, M.; Pei, J. C. (2017)
    To explore the nature of collective modes in weakly bound nuclei, we have investigated deformation effects and surface flow patterns of isovector dipole modes in a shape-coexisting nucleus, Mg-40. The calculations were done in a fully self-consistent continuum finite-amplitude quasiparticle random phase approximation in a large deformed spatial mesh. An unexpected result of pygmy and giant dipole modes having disproportionate deformation splittings in strength functions was obtained. Furthermore, the transition current densities demonstrate that the long-sought core-halo oscillation in pygmy resonances is collective and compressional, corresponding to the lowest excitation energy and the simplest quantum flow topology. Our calculations show that surface flow patterns become more complicated as excitation energies increase.
  • Orlandi, R.; Mucher, D.; Raabe, R.; Jungclaus, A.; Pain, S. D.; Bildstein, V.; Chapman, R.; de Angelis, G.; Johansen, J. G.; Van Duppen, P.; Andreyev, A. N.; Bottoni, S.; Cocolios, T. E.; De Witte, H.; Diriken, J.; Elseviers, J.; Flavigny, F.; Gaffney, L. P.; Gernhauser, R.; Gottardo, A.; Huyse, M.; Illana, A.; Konki, J.; Kroll, T.; Krucken, R.; Lane, J. F. W.; Liberati, V.; Marsh, B.; Nowak, K.; Nowacki, F.; Pakarinen, J.; Rapisarda, E.; Recchia, F.; Reiter, P.; Roger, T.; Sahin, E.; Seidlitz, M.; Sieja, K.; Smith, J. F.; Dobon, J. J. Valiente; Von Schmid, M.; Voulot, D.; Warr, N.; Wenander, F. K.; Wimmer, K. (2015)
  • Pei, J. C.; Wang, Kai; Kortelainen, M. (IOP Publishing, 2018)
    Journal of Physics Conference Series
    In order to explore the nature of collective modes in weakly bound nuclei, we have investigated surface flow patterns of isoscalar monopole modes in a shape-coexisting nucleus Mg-40. The calculations were done in a fully self-consistent continuum finite-amplitude-method quasiparticle-random-phase-approximation (FAM-QRPA) in a large deformed spatial mesh. Our results demonstrated that the transition current densities at surfaces are nontrivial and dependent on deformations. The toroidal mode is favorable in the oblate shape, demonstrating the geometric deformation effects on nuclear surface flows. The surface flow patterns become more complicated as excitation energies increase.